It is well known that collated books are often bound using a helical coil which passes through aligned holes at one edge of the book. This provides a book which can be easily opened and held at an opened position and is therefore particularly effective for manuals and reference materials.
The helical coil at the edge of the book can be formed from a coiled wire or a coiled strip of plastic material. Coiled wire has the significant advantage that it can be more easily inserted. Helical plastic coil has the advantages that it can be manufactured in different colours and therefore provides a particularly attractive appearance as opposed to the strictly utilitarian appearance of the steel wire.
Helical coils are produced by rotating the plastic material on a mandrel. The material is heated in order to adopt the diameter and pitch achieved by the mandrel. Mandrels are commonly an elongate rod which has a stationary coil guide that guides the material along the rod such that the material adopts the pitch of the coil guide and the diameter of the rod.
After forming the coils are inserted into the aligned holes at the edge of a collated book for binding the book. This can be carried out manually where the operator has control over the book and the coil to ensure proper insertion. However such manual processes are relatively slow and therefore expensive.
In U.S. Pat. No. 6,000,897 of Desjarlais issued Dec. 14, 1999 is disclosed a machine for inserting a plastic coil into aligned holes at the edge of a book for binding of the book.
Also in U.S. Pat. No. 7,246,982 of Desjarlais and Klassen issued Jul. 24, 2007 is disclosed a number of operating improvements to this machine.
This machine has achieved considerable commercial success and has operated successfully in the insertion of plastic coils automatically.
Also in U.S. Pat. No. 6,382,950 of Desjarlais and Klassen issued May 7, 2002 is disclosed a machine for winding the helical coil.
The disclosures of each of the above three patents are incorporated herein by reference or should be reviewed for further information concerning the techniques for manufacturing and inserting plastics coil of the type with which the present invention is concerned.
One of the issues with the use of coils formed from plastics material is that if the increased difficulty of insertion into the book relative to that of metal wire. This still leaves to some resistance amongst users to the use of such plastics coil despite the increased attractiveness of the product.